201. Sheetal, 39-yrs-old presents with chronic abdominal cramps, watery diarrhea, and periodic facial flushing. Examination reveals wheezing and a slightly enlarged liver. Work up reveals several masses within the liver and a large mass in the small intestine. Which of the following substances is likely to be elevated in her urine?

S-hydroxyindoleacetic acid(S-HIAA) The patient shows signs of the carcinoid syndrome, which include flushing, diarrhea, and bronchoconstriction. * The syndrome results from elaboration of serotonin (5-hydroxytryptamine) by a primary carcinoid tumor in the lungs or ovary or from hepatic metastases from a primary carcinoid tumor in the gastrointestinal tract. However, primary appendiceal carcinoid tumors, the most common gastrointestinal carcinoid tumors, very rarely metastasize and are viually always asymptomatic. * Carcinoid tumors arise from cells of the neuroendocrine system, which, as pa of the, amine precursor uptake and decarboxylation (APUD) system, are capable of secreting many products, * Grossly, carcinoid tumors, which tend to be multiple when they occur in the stomach or intestines, are characteristically solid and firm and have a yellow-tan appearance on sectioning, * Histologically they are composed of nests of relatively bland-appearing monotonous cells. Diagnosis is based on finding increased urinary 5-hydroxyindoleacetic acid (5-HIAA) excretion from metabolism of excess serotonin. * In contrast, increased urinary levels of aminolevulinic acid (ALA) are seen with lead toxicity, increased N- formiminoglutamate (FIGLU) with folate deficiency, and increased normetanephrine or vanillylmandelic acid (VMA) with tumors of the adrenal medulla (pheochromocytoma in adults and neuroblastoma in children).